Development Of Distributed Tunnel Seismic Exploration System

With the rapid development and continuous progress of China's national economy,the country has begun to attach great importance to the construction of transportation infrastructure.However,in some areas of China,the terrain is complex.Therefore,with the increase of tunnel engineering,the construction difficulty also increases gradually.In the process of tunnel construction,it is impossible to accurately predict faults,karst caves,broken rock masses,groundwater and other unfavorable geological bodies along the tunnel,which is the main cause of geological disasters such as landslides and water inrush.As far as the current domestic research status is concerned,tunnel construction safety awareness is generally weak.Therefore,it is of great importance to carry out advanced tunnel prediction,formulate reasonable construction plan and take corresponding measures according to the forecast results,to reduce the probability of geological disasters and eliminate the hidden safety hazards.In this paper,a feasible scheme of distributed tunnel seismic exploration system is proposed from the seismic exploration method,based on the theory of the seismic wave reflection method and the construction methods of the TSP method and the TVSP method for the tunnel advance prediction system.And a tunnel advance prediction system with low internal noise,large dynamic range,strong weak signal detection ability,small size and convenient construction is developed based on the scheme.In this system,a distributed observation system is formed by cascades of samplers in three channels.The number of samplers can be selected according to the demand,and the number of explosive points can be reduced,so as to effectively improve the work efficiency,reduce the construction risk.The short-circuit trigger mode is added on the basis of the traditional open-circuit trigger mode,which supports the vibriosis,can ensure the consistency of the source signal,make up for the lack of explosive source blasting in the safety sensitive area,and has higher safety performance.The distributed tunnel seismic exploration system mainly consists of two parts: hardware circuit design and software program development.The hardware circuit uses STM32F429 as the main controller,combined with an FPGA chip,Ethernet transceiver circuit,data storage circuit and drive acquisition circuit,so that the whole system has the function of acquisition and self-test.The software program is developed by migrating the FreeRTOS embedded real-time operating system,and the LWIP protocol stack based on Atollic platform,and designing the bottom drivers and data interaction programs to realize system's control,data acquisition and transmission functions.Finally,the basic performance test and field experiment of the distributed tunnel seismic exploration system are carried out.After testing,the system modules can run normally,the data transmission is stable and reliable,and the system performance index has reached the expected target.The noise level of the system is lower than 12 ?V,the dynamic range is up to 110 dB,the sampling frequency is up to 64 KHz,the acquisition time is longer than 30 minutes,and the Ethernet average transmission rate is up to 2.82 MB/s.